Candidate BH Obama Mitt Romney
Running mate Joe Biden Paul Ryan
Electoral vote 332 206
States carried 26 + DC 24
Popular vote 65,907,213 60,931,767
Percentage 51.1% 47.2%
Even if ALL four million (referred to stayed at home) had voted for Romney he STILL would have lost.
I think you'll find that a detailed analysis will show that a residual platoon of diehard Rockefeller Republicans didn't vote for Romney and that made all the difference.